Project Summary Broad Impact: The Medial Superior Olive (MSO) detects differences in the arrival time of sounds between the two ears to compute the sounds location (Interaural time difference, ITD). MSO neurons are highly specialized to detect these microsecond differences in timing. While the MSO's ability to detect ITDs of simple sounds, such as tones, is well understood, little work has been done investigating how ITDs of more complex/naturalistic sounds are detected. Preliminary data from our lab shows that there are groups of neurons in the MSO with different physiological properties from typical ?principal? MSO neurons. The overarching goal of this proposal is to discover the roles of these new cells in sound localization using a combination of in vivo and in vitro techniques. Aim 1A: Perform in vivo patch experiments to determine the functional role of new cell types by recording their responses when different sound stimuli are presented. Aim 1B: in vitro patch experiments in brain slices to characterize the synaptic properties of these new cell types and to compare these properties to known principal cell properties. Aim 2: Use activity-dependent viral labeling techniques to examine the organization of these new cell types. These experiments will reveal the role these previously described neurons have in the sound localization circuit and greatly expand the field's understanding of how the MSO processes sound location. Training: This project will teach the applicant several new techniques, including in vivo patch clamp, using viral tools, and histology/imaging. Additionally, the applicant will have the opportunity to participate in both local and international collaborations with other labs. This proposal will aid the applicant in disseminating his work to the scientific community through conferences presentations and journal publications, as well as provide him with skills for his future in the academic field.